I like the Hitec titanium servos because they are so indestructible. I have a Spektrum H6040(Savox 1258) on gas in my DM-1, and so far so good((Hobbico CS170 on steering) Fast and strong enough, at least for gas. Had an ACE DS1015 in my RC8B and it was great too..

Phil, those servos I recommended are very good choices IMHO. There are others, but those are two very good relatively affordable ones. Only question is if you want to run lipo receiver batteries at some point(for me anyway, unnecessary..)